rational
rational — 形容詞
1. involving decisions, beliefs, or actions that are based on facts and careful thi
理智的
根據事實和邏輯而非情緒的
involving decisions, beliefs, or actions that are based on facts and careful thinking rather than on feelings or personal wishes
Lisa made a rational choice to leave early and avoid the traffic.
Lisa 提早離開避開車流，這是個理智的選擇。
collocation: rational choice
It is not always rational to let fear guide your decisions.
讓恐懼主導你的決定，不一定總是合理的。
impersonal: it is rational to do something
The manager asked for a rational explanation of the budget problem.
經理要求就預算問題提出合理的解釋。
Wei's argument was clear, rational, and supported by strong evidence.
Wei 的論點清晰明理，且有充分證據支持。
There was no rational reason for closing the school during the storm.
颳風期間關閉學校，沒有任何合理的理由。
- reasonable
more general; can apply to prices, amounts, and expectations, not just decisions
- logical
emphasises step-by-step reasoning and consistency rather than practical good sense
- sensible
practical and showing good judgment, with less emphasis on formal reasoning
- irrational
the direct opposite; based on emotion rather than reason
- emotional
driven by feelings, the opposite of detached logical thought
- unreasonable
not fair or sensible; often used for demands or expectations
文法句型
rational + noun
be rational to + infinitive
rational about + noun phrase
用法筆記
Evaluates specific choices, decisions, or arguments rather than a person's general thinking capacity — compare sense 2 (REASONING CAPACITY). Frequently used in the pattern 'it + be + rational + to-infinitive'.
常見錯誤
2. having the ability to think clearly, understand ideas, and make judgments based
理性的
具備邏輯思考與判斷能力的
having the ability to think clearly, understand ideas, and make judgments based on logic rather than feelings or instincts
Human beings are rational creatures who can plan for the future.
人類是有理性的生物，能夠計劃未來。
collocation: rational creatures
Theo was too upset to be rational about what had happened.
Theo 太難過了，無法理性思考所發生的事情。
rational about + noun clause
Even young children show some rational thinking when solving simple puzzles.
即使是年幼的孩子，在解決簡單謎題時也會展現出一些理性思考。
A rational person considers the results of their actions before acting.
一個理性的人會在行動之前考慮行為的後果。
The court decided that the patient was not rational at the time of the accident.
法院判定該患者在事故發生時並不具備理性判斷能力。
- thinking
broader; describes any cognitive activity, not necessarily logical
- intellectual
emphasises the use of intellect and knowledge, often in academic contexts
- reasoning
emphasises the process of drawing conclusions from evidence
- irrational
lacking the ability to think logically; driven by instinct or emotion
- instinctive
based on natural impulse rather than reasoned thought
文法句型
rational + noun (being, creature, mind)
be rational about + noun phrase
not rational + adverbial
用法筆記
Describes beings (usually human) who possess the general capacity to think and reason. Compare sense 1 (LOGICAL THINKING), which evaluates individual actions rather than the person's overall faculty. In legal and medical contexts, 'not rational' can refer to a temporary state where judgment is impaired.
常見錯誤
3. describes any number you can write as a fraction made from two integers, like 1/
有理數的
可用兩個整數比值表示的數字
describes any number you can write as a fraction made from two integers, like 1/2, 3/4, or 7
Every whole number is rational because it can be written as a fraction.
每個整數都是有理數，因為它可以寫成分數。
predicative use with because-clause
Ishaan learned to add rational numbers like one half and three quarters.
Ishaan 學到了如何加總像二分之一和四分之三這樣的有理數。
collocation: rational numbers
The number 0.75 is rational because it equals three quarters.
0.75 是有理數，因為它等於四分之三。
Salma had to decide whether each number was rational or irrational.
Salma 必須判斷清單上的每個數是有理數還是無理數。
- fractional
narrower; refers only to fractions, not whole numbers
- arithmetic
broader; describes any number used in basic calculations
- irrational
of a number that cannot be written as a fraction, such as π or √2
文法句型
rational + noun (number, expression)
用法筆記
Used only in mathematics. Never describes people or behavior. The opposite is irrational (a number that cannot be written as a simple fraction, such as π or √2).
常見錯誤
rational — 名詞
1. a number you can show as a simple fraction made from a pair of integers, such as
有理數
可用兩個整數比值表示的數
a number you can show as a simple fraction made from a pair of integers, such as 2, 1/3, or 0.75
All integers are rationals because each can be written over one.
所有整數都是有理數，因為每個整數都可以寫成分母為一的分數。
plural form: rationals
The teacher asked the class to list five rationals between one and two.
老師要求全班列出介於一到二之間的五個有理數。
use with quantity: five rationals
Soraya explained that a repeating decimal is also a rational.
Soraya 解釋說循環小數也是有理數。
Decimals that end are rationals, while some others go on forever.
能除盡的小數是有理數，而有些小數則會無限延伸下去。
- rational number
the full, formal term; 'rational' by itself is an abbreviation used in math contexts
- irrational
a number that cannot be written as a fraction of two whole numbers
文法句型
a rational
rational + plural -s
用法筆記
Used mostly in mathematics textbooks and classroom settings. The plural form is 'rationals'. When spoken, the word sounds the same as the adjective — /ˈræʃ.nəl/ — so context determines the part of speech.